MSG_CHILD_FD_RECEIVED
AWAIT_INT_MESSAGE(sock_fds[1], MSG_CHILD_FD_RECEIVED);
SEND_INT_MESSAGE(sock_fds[0], MSG_CHILD_FD_RECEIVED);
SEND_INT_MESSAGE(sock_fds[0], MSG_CHILD_FD_RECEIVED);
AWAIT_INT_MESSAGE(sock_fds[1], MSG_CHILD_FD_RECEIVED);